Ammuntion safety device



INVENTOR ATTORNEY March 1965 c. o. J. NORDZELL AMMUNITION SAFETY DEVICE Filed May 24, 1962 1 H llnrfwfwlqldfh v VII/ CARL OLOF JULIUS NORDZELL United States Patent Office 3,173,364 Patented Mar. 16, 1965 3,173,364 AMMUNITION SAFETY DEVICE Carl Olof Julius Nordzell, Lidingo, Sweden, assignor to Military Training Device Company, Stockholm, Sweden, a corporation of Sweden Filed Mar. 24, 1962, Ser. No. 197,420 4 Claims. (Cl. 102-1) If a body charged with an explosive, such as a projectile the explosive of which is completely enclosed in a fireresistant strong shell, is heated by fire or in any other way to a critical temperature the charge will detonate more or less completely. An explosive such as T.N.T., having a melting point of about 80 C., will, in melting, expand about 10%. If the explosive is completely enclosed in a cover that will not burst or open itself in another way, a more or less complete detonation will occur. It has been observed that molten T.N.T. will be forced out through screw holes and be ignited. This will usually occur some minutes before the detonation. The pressure is here estimated to be about 1,000 kilograms per square centimeter.

If on the other hand the shell is provided with a sufliciently large venting opening the charge may wholly or partly burn or melt out of the shell without detonating. Such a venting opening may be provided by removing the closure (detonating fuze, detonator closing cover or the like) or by providing a burnable or meltable closure. For storage purposes or in military emergencies, said measure may be less desirable, or the venting opening thus provided may be too small.

The main object of the present invention is to be applied in such latter cases. According to the invention a protective explosive charge which can be ignited under the influence of heat is arranged close to the shell or to a closed opening thereof in such a way that said protective charge at the igniting temperature is caused to burst or to blast up part of said shell or open said closure respectively without causing the main charge to detonate or in any case to detonate incompletely only and thus with a sufficiently reduced effect.

One embodiment of the invention as illustrated in connection with a projectile is shown diagrammatically in a longitudinal section in the accompanying drawing.

The shell 1 of the projectile contains a main charge 2 with detonator 2a arranged adjacent the top of the projectile said top being closed by a closure 3 which may be provided with a handle, and is made of a material having a good thermal conductivity or being provided with an igniting channel. A detonating charge 4 arranged in the closure is provided with a temperature sensitive igniter and with an explosive having a higher melting point than said main charge. A protective or top charge 5 is inserted close to the detonating charge 4, and preferably the explosive of the top charge may have a higher melting point than the main charge. Further, a protective body 6 of a suitable material such as wood, plastic, cork, metal or the like is provided to prevent or obstruct the detonation wave from the top charge 5 from being transmitted to the detonator 2a and the main charge 2.

When the projectile is exposed to heat, for instance through fire the detonating charge 4 will be ignited causing the top charge 5 to detonate thereby opening the top of the projectile or causing the shell 1 to burst before the main charge 2 is detonated. The release time is usually one to four minutes from the beginning of a heavy fire, but may be as much as eight minutes in one practical embodiment tested. This provides an adequate safety margin because unpacked shells normally detonate spontaneously after ten to fifteen minutes and shells having wooden packing in about twenty to twenty-five minutes. By detonation of top charge 5, a sufi'iciently large opening will be formed to allow the main charge during continued heating to burn Wholly or partly or to melt without detonating. Preferably, the parts 3 to 6 according to the invention may form a unit which easily may be inserted into the top opening 7 of the projectile. Said parts may for instance be housed in a sleeve 8.

Instead of heating the detonating charge 4 by means of thermal conductivity of the closure 3 the latter may be provided with an igniting channel 9 having a melting seal 10 which melts at the critical temperature and leaves the channel open thereby causing the detonating charge to be directly exposed to the high outer temperature or to a flame from a fire or the like. In this case the detonating charge 4 may comprise a low explosive, the melting point of which does not need to be higher than that of the main charge.

The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come Within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by United States Letters Patent is:

1. In combination with a shell filled with a high explosive main charge, a safety device for preventing unintended, heat induced detonation of the explosive main charge, comprising:

(a) a protective explosive charge in said shell, said charge being large enough that its detonation will create a venting opening in said shell of sufficient size to allow the main charge to burn or flow out of the shell without high order detonation; and

(b) means responsive to the heating of said shell and operable at a temperature below the detonation temperature of the main charge for detonating the protective charge and thereby creating said venting opening in said shell.

2. The combination as defined in claim 1, wherein:

(a) said shell has a normally sealed opening at one end thereof; and

(b) the protective explosive charge is located adjacent said Opening.

3. The combination as defined in claim 1, wherein said protective charge detonating means is in thermal contact with said shell.

4. The combination as defined in claim 1:

(a) wherein said shell has an opening at one end thereof; and

(b) said safety device includes a closure for said opening, means forming a protective charge ignition channel in said opening, and a seal in said channel of a normally solid material having a melting point lower than the detonation temperature of the main charge in said shell.

References Cited in the file of this patent UNITED STATES PATENTS 

1. IN COMBINTION WITH A SHELL FILLED WITH A HIGH EXPLOSIVE MAIN CHARGE, A SAFETY DEVICE FOR PREVENTING UNINTENDED, HEAT INDUCED DETONATION OF THE EXPLOSIVE MAIN CHARGE, COMPRISING: (A) A PROTECTIVE EXPOSIVE CHARGE IN SAID SHELL, SAID CHARGE B EING LARGE ENOUGH THAT ITS DETONATION WILL CREATE A VENTING OPENING IN SAID SHELL OF SUFFICIENT SIZE TO ALLOW THE MAIN CHARGE TO BURN OR FLOW OUT OF THE SHELL WITHOUT HIGH ORDER DETONATION; AND (B) MEANS RESPONSIVE TO THE HEATING OF SAID SHELL AND OPERABLE AT A TEMPERATURE BELOW THE DETONATION TEMPERATURE OF THE MAIN CHARGE FOR DETONATING THE PROTECTIVE CHARGE AND THEREBY CREATING SAID VENTING OPENING IN SAID SHELL. 